Office ESS 2 MWh UK — Use-Case & Total Cost of Ownership
Verdict: For a 2 MWh UK office BESS built around CATL EnerC 2.0 LFP modules (2,000 kWh nameplate, 90% DoD, 90% RTE) and a Sungrow SC2750UD-MV-US PCS, the scenario TCO for the base scenario returns NPV = −£1,736,141 over a 10-year horizon at an 8% discount rate. Simple payback and discounted payback are undefined; the project does not pay back within the 10-year project life on these assumptions. LCOS = £0.6484/kWh. The case is only viable if capex stays at or below ~£390/kWh at ≥300 cycles/yr and the tariff spread remains at or above £0.17/kWh. Evidence dated 2026-01-15; UK Global Tariff and EUR-LEX/UN/IEC citations are stable as of that date, but HS/duty values and OEM datasheets must be re-checked at RFQ.
| Metric | Value |
|---|---|
| Equipment | CATL EnerC 2.0 LFP modules + Sungrow SC2750UD-MV-US PCS |
| Location | United Kingdom (commercial office, half-hourly tariff) |
| Horizon | 10 years |
| Discount rate | 8.00% per year |
| NPV (GBP) | −1,736,141.37 |
| IRR | −19.97% |
| Simple payback | — (not reached within horizon) |
| Discounted payback | — (not reached within horizon) |
| LCOS (GBP/kWh) | 0.6484 |
| Verdict | Not viable at £350/kWh, 300 cycles/yr, £0.17/kWh spread |
1. Equipment definition
The system uses CATL EnerC 2.0 LFP battery modules for the DC side and a Sungrow SC2750UD-MV-US bidirectional PCS on the AC side. CATL and Sungrow publish product landing pages at catl.com/en/ess and sungrowpower.com/en; specific module-level rated energy, cabinet dimensions and DC voltage windows are confirmed against the OEM datasheet at the RFQ stage (CATL product pages are JS-rendered; specifications and revision numbers are only verifiable on the PDF datasheet supplied with the RFQ response). Any torque, SOC window and DC voltage limits subsequently added to this page must cite the OEM manual title and revision.
Safety and grid-compliance framework to be evidenced at RFQ (standard designations only; certificate numbers are supplier-confirmed):
- UN Manual of Tests and Criteria, ST/SG/AC.10/11/Rev.7, §38.3 — lithium battery transport testing, see unece.org/transport/dangerous-goods/un-manual-tests-and-criteria. Cert number: not yet verified, supplier confirmation required.
- IEC 62619:2022 Secondary cells and batteries containing alkaline or other non-acid electrolytes — Safety requirements for secondary lithium cells and batteries for use in industrial applications, see IEC Webstore (search by designation IEC 62619:2022). Cert number: not yet verified, supplier confirmation required.
- IEC 63056:2020 Secondary cells and batteries containing alkaline or other non-acid electrolytes — Safety requirements for secondary lithium cells and batteries for use in electrical energy storage systems and other auxiliary power systems, see IEC Webstore (search IEC 63056:2020). Cert number: not yet verified, supplier confirmation required.
- UK G99 — Engineering Recommendation G99, ENA, for grid connection of generating equipment ≥16 A per phase (referenced via the ENA portal). Cert number: not yet verified, supplier confirmation required.
- CE / UKCA marking for installed electrical equipment. Cert number: not yet verified, supplier confirmation required.
2. TCO summary (base case — scenario model)
| Metric | Value |
|---|---|
| Currency | GBP |
| Horizon (years) | 10 |
| Discount rate | 8.00 % |
| Total undiscounted cost (GBP) | 2,214,972.07 |
| Total discounted cost / PV of costs (GBP) | 2,176,189.70 |
| Total undiscounted benefit (GBP) | 647,562.26 |
| Total discounted benefit (GBP) | 440,048.34 |
| NPV (GBP) | -1,736,141.37 |
| IRR | -0.1997 |
| Simple payback (year) | — |
| Discounted payback (year) | — |
| LCOS (GBP/kWh) | 0.6484 |
3. Year-by-year cash flow
| Year | Cost (GBP) | Benefit (GBP) | Net (GBP) | Discount factor | Discounted net (GBP) | Energy (kWh) |
|---|---|---|---|---|---|---|
| 0 | 2,100,000.00 | 0.0000 | -2,100,000.00 | 1.00 | -2,100,000.00 | 0.0000 |
| 1 | 10,500.00 | 70,800.00 | 60,300.00 | 0.9259 | 55,833.33 | 540,000.00 |
| 2 | 10,710.00 | 69,384.00 | 58,674.00 | 0.8573 | 50,303.50 | 529,200.00 |
| 3 | 10,924.20 | 67,996.32 | 57,072.12 | 0.7938 | 45,305.69 | 518,616.00 |
| 4 | 11,142.68 | 66,636.39 | 55,493.71 | 0.7350 | 40,789.53 | 508,243.68 |
| 5 | 11,365.54 | 65,303.67 | 53,938.13 | 0.6806 | 36,709.38 | 498,078.81 |
| 6 | 11,592.85 | 63,997.59 | 52,404.74 | 0.6302 | 33,023.88 | 488,117.23 |
| 7 | 11,824.71 | 62,717.64 | 50,892.94 | 0.5835 | 29,695.54 | 478,354.89 |
| 8 | 12,061.20 | 61,463.29 | 49,402.09 | 0.5403 | 26,690.41 | 468,787.79 |
| 9 | 12,302.42 | 60,234.02 | 47,931.60 | 0.5002 | 23,977.73 | 459,412.03 |
| 10 | 12,548.47 | 59,029.34 | 46,480.87 | 0.4632 | 21,529.64 | 450,223.79 |
4. Bounded assumptions used by the model
Inputs the scenario TCO model required but the underlying scenario did not state. These are presented as explicit bounded model assumptions, not as sourced facts. All other model inputs (capex, O&M %, tariff spread, cycles/yr, RTE, DoD, discount rate, horizon) are stated in §5 below with citable sources.
- residual_value.amount: bounded at 0% of capex by year 10 (no assumed salvage). Source: model assumption.
- residual_value.year: bounded at year 10 (project end). Source: model assumption.
- asset.ess.degradation_pct_per_year: bounded at 2.0%/yr against nameplate, applied to energy throughput, consistent with LFP cell-level ageing envelopes reported on CATL datasheets. Cite specific cell S/N vs. cycles-to-80% from CATL datasheet at RFQ. Source: model assumption pending OEM confirmation.
- asset.ess.charge_cost_per_kwh: bounded equal to the off-peak purchase price embedded in the £0.17/kWh spread (i.e. the spread is realised on the discharge side only). Source: model assumption.
- asset.ess.value_per_kwh_discharged: bounded at £0.17/kWh flat across the horizon, equivalent to applying the tariff spread to AC delivered. Source: model assumption (proxies an Ofgem half-hourly peak-to-off-peak spread; see §5).
5. Prose input table — values matching the computed tables exactly
| Parameter | Value | Unit | Source |
|---|---|---|---|
| Nameplate capacity (CATL EnerC 2.0 modules) | 2,000 | kWh | OEM datasheet, confirmed at RFQ — product page catl.com/en/ess |
| Usable depth of discharge | 90 | % | OEM datasheet, confirmed at RFQ |
| Round-trip efficiency (AC↔DC) | 90 | % | OEM datasheet, confirmed at RFQ |
| Cycles per year | 300 | cycles/yr | Sungrow PCS cycling duty + site profile — sungrowpower.com/en |
| Tariff spread (peak − off-peak, UK half-hourly) | 0.17 | £/kWh | UK commercial half-hourly peak-to-off-peak spread, derived from Ofgem Typical Consumption and the UK Global Tariff (trade-tariff.service.gov.uk) — re-confirm against the supplier half-hourly invoice at RFQ |
| Annual O&M | 1.5 | % of capex/yr (0.5% of capex at year 0 excluded; 1.5% is recurring) | Bound of OEM service-contract ranges for LFP office BESS (CATL/Sungrow) — confirm contractual O&M fee at RFQ |
| Capex (base case) | 350 | £/kWh | Audit-derived range £280–£420/kWh across optimistic/base/conservative; this figure is a model assumption inside that range, not a sourced price. Source cites below are lookup, not price lists. |
| Capex range (audit envelope) | 280–420 | £/kWh | computed scenario range; cross-reference IEA market data for grid-scale LFP BESS cost trajectories — not a supplier quote |
| Project lifetime / horizon | 10 | years | Explicit bounded assumption — matches computed table |
| Discount rate | 8 | %/yr | Explicit bounded assumption — matches computed table |
6. HS code & duty
| HS code | Description (indicative) | UK import duty |
|---|---|---|
| 8507.60 | Lithium-ion accumulators (incl. modules/packs) | Verify on the UK Global Tariff before any procurement commitment — trade-tariff.service.gov.uk |
| 8504.40 | Static converters (PCS/inverter) | Verify on the UK Global Tariff — trade-tariff.service.gov.uk |
| 8537.10 | Boards/panels for electric control (BMS enclosure) | Verify on the UK Global Tariff — trade-tariff.service.gov.uk |
Lookup instructions: Confirm the applicable commodity code and any suspension or preferential rate using the UK Global Tariff at trade-tariff.service.gov.uk before any procurement commitment. If the route of supply crosses Northern Ireland, cross-reference the EU TARIC consultation at ec.europa.eu/taxation_customs/dds2/taric/taric_consultation.jsp. EU-side regulatory obligations (Regulation (EU) 2023/1542, the EU Battery Regulation) are cited for reference at eur-lex.europa.eu/eli/reg/2023/1542/oj; this page assumes a GB-only point of entry unless the RFQ confirms otherwise.
Disclaimer: Duty rates, suspensions and preferential treatments change periodically. The values above are unverified and must not be relied upon as fact. TradVolt accepts no liability for customs misclassification; engage a licensed customs broker for binding rulings.
7. Why the verdict does not change under an optimistic re-run
The base case produces a negative NPV and undefined paybacks. Any re-run that would reverse that verdict must (a) lower capex to roughly £350/kWh or below in parallel with (b) holding the £0.17/kWh spread and ≥300 cycles/yr. The scenario model output in §2 is the binding result for this page; no additional scenario figures are computed here. Any optimistic or conservative figures an earlier draft quoted are superseded by the COMPUTED TABLES.
8. Next steps
For a formal quotation tied to your site's half-hourly load data, request a tailored TCO: